In the treatment of a cerebral aneurysm, since the blood vessel system in the brain is structurally complicated, it is difficult to accurately assess the structure and nature of the lesion using typical angiography. Thus, it is desired to represent the blood vessels three-dimensionally. X-ray angiography apparatus check condition of a blood vessel in the body of a patient by inserting a catheter into the blood vessel, injecting a contrast medium, and taking X-ray radiographs using angiography. With the X-ray angiography apparatus, blood vessel images shot by an X-ray radiography apparatus are transmitted to a medical image processing apparatus, reconstructed into three-dimensional image data by the medical image processing apparatus, and displayed on a monitor as 3D-DSA (Digital Subtraction Angiography) images. An observation angle of the blood vessel can be changed by rotating the 3D-DSA image on the monitor of the medical image processing apparatus using a mouse or the like.
Once the observation angle of the blood vessel is determined on the 3D-DSA image displayed on the monitor of the medical image processing apparatus, the observation angle is transmitted to the X-ray radiography apparatus. A radiography unit of the X-ray radiography apparatus moves to a position corresponding to the received observation angle. This function is called “angle feedback.”
Generally, X-ray angiography apparatus for cerebral blood vessels are often a biplane type capable of taking angiograms simultaneously from two directions using two radiography systems. A radiography system set up in a front direction of an object laid face-up on a patient table is referred to as a frontal radiography system and a radiography system set up in a lateral direction of the object is referred to as a lateral radiography system.
The frontal radiography system includes a C-arm supported by a floor-mounted stand as well as an X-ray tube and X-ray detector mounted at opposite ends of the C-arm. The lateral radiography system includes a Ω-arm suspended from a ceiling as well as an X-ray tube and X-ray detector mounted at opposite ends of the Ω-arm.
Japanese Patent Laid-Open No. 9-187448 discloses a technique for performing quantitative analysis of an object's area to be diagnosed based on an image shot by biplane angiography and correcting results of the quantitative analysis using geometric magnification.
In the case of biplane angiography, to set both frontal and lateral radiography systems to appropriate observation angles, it is necessary to set the angles from an external apparatus. However, conventionally the “angle feedback” function works only in a single direction. Consequently, for example, if the observation angle of only the frontal radiography system is set using the “angle feedback” function, the observation angle of the lateral radiography system to be set is found using a 3D-DSA image and then the arm is set manually. This is very troublesome. Also, since both the frontal radiography system and lateral radiography system are moved, there is a problem of interference depending on positions of the two systems. In particular, when the angle of the lateral radiography system is set manually, it is difficult to find angles at which interference occurs. This makes it necessary to change the angle each time interference occurs.